1. Field of the Invention
The present invention relates to an image forming apparatus that is capable of accessing a removable storage medium and a method of controlling the image forming apparatus.
2. Description of the Related Art
A printer or multifunction peripheral that expresses colors using color toner or the like is required to perform the calibration of a printer engine so as to perform faithful color reproduction. Particularly, most products which include a printer engine that performs image formation on a medium by an electrophotographic process have a calibration function because the degree of adherence of toner of each color to the medium varies depending on the temperature and humidity of the surrounding environment and conditions of a photosensitive member within the engine.
Hereafter, a description will be given of an example of a procedure of execution of the calibration of the printer engine that employs the electrophotographic process. First, images for density measurement, each of which is called a patch, are formed on an intermediate transfer member of the engine. Assuming cases of several levels of output density, there are formed a plurality of patches in which toner is attached in amounts associated with the respective levels of the patch density. Next, color measurement is performed on the patches by a sensor equipped in the engine, and the differences between the patch densities for realizing the best color reproduction and the actually measured patch densities are calculated. The calibration is accomplished by adjusting laser intensity and controlling printer engine operations including image processing such that the differences are minimized.
The printer or multifunction peripheral that has just been calibrated is adjusted to a state in which the printer engine is capable of reproducing colors with the utmost accuracy. Then, as the number of printed sheets increases thereafter, the printed colors gradually come to deviate from those obtained immediately after the calibration. In a case where a highly accurate color reproduction is demanded of printout, it is desirable to execute printing immediately after the calibration.
However, in general, the calibration is performed only with a predetermined frequency specific to each product of the printer or multifunction peripheral, and when a highly accurate color reproduction is demanded of printout, the engine is not always in a state capable of performing the best color reproduction. To solve this problem, for example, Japanese Patent Laid-Open Publication No. 2000-227684 discloses a technique in which the calibration is automatically started when a print job is input by a user from a host computer.
In the technique disclosed in Japanese Patent Laid-Open Publication No. 2000-227684, if a specific print mode is set, it is possible to forcibly perform the calibration when a print job is input, and hence when a printing operation is started, the engine is ready for performing the best color reproduction.
The method of inputting a print job to a printer or multifunction peripheral includes conventionally proposed methods described hereafter.
For example, in the method disclosed in Japanese Patent Laid-Open Publication No. 2000-227684, a user of a network-connected or serial-connected host computer selects a file, and then inputs a print job for printing the file to a printer or multifunction peripheral. In this case, it takes several tens of seconds or several minutes before the calibration of the printer or multifunction peripheral to which the print job is input is completed after the calibration is started when the user selects the printer or multifunction peripheral.
Further, there has also been proposed a method in which a user of a printer or multifunction peripheral, which is equipped with a unit adapted to recognize a removable memory device inserted therein, designates one of files stored in the inserted memory device, and inputs the selected file to the printer or multifunction peripheral. This method is applied to printers or multifunction peripherals having a so-called memory direct printing function.
Particularly, in recent years, there is an increasing demand for memory direct printing which is configured to be performed by inserting into a printer a memory card storing images captured by a digital camera. Further, it becomes popular to store and carry electronic document files in a memory card or a USB flash memory, and it is also envisaged to use memory direct printing for printing out such office documents under circumstances where no computer is available.
However, even in the case of using memory direct printing, a print job is input after the user selects a file. Therefore, timing of starting the calibration is the same as in the case where the print job is input from the network-connected or serial-connected host computer. Therefore, the user performing memory direct printing is required to wait for several tens of seconds or several minutes before the calibration is completed after inputting the print job.